The objective of the proposed research plan is to further the development of the technology demonstrated in Phase I for automated real-time feedback control of laser lithotripsy. In vitro results to date have shown considerable promise for utilizing the characteristic prompt optical emissions generated during pulsed laser lithotripsy for the rapid automatic feedback control of laser energy delivery. The result is a technique which can significantly reduce the risk of laser injury to healthy soft tissue while maintaining good stone fragmentation efficacy. The need for such a device is increasingly evident as laser pulse energies used clinically have increased in order to treat the hardest stones. Further, such a device would be invaluable under conditions where direct vision is problematic (such as occurs in the biliary tree). The specific aims of the Phase II effort are: 1) incorporate the feedback control device into a commercial (or investigational) pulsed dye laser lithotriptor, 2) demonstrate the efficacy and improved safety of this "smart" device in a series of in vivo studies performed in pigs, and 3) establish final design specifications based on results of item 2 and input from clinician users and the laser manufacturer(s).